Planetary habitability involves orbiting at the right distance from the host star for liquid surface water to be present, in addition of various geophysical and geodynamical aspects, atmospheric density, radiation type and intensity, and the host star's plasma environment.[2]

In astronomy and astrobiology, the circumstellar habitable zone (CHZ or sometimes "ecosphere", "liquid-water belt", "HZ", "life zone" or "Goldilocks zone") is the region around a star where a planet with sufficient atmospheric pressure can maintain liquid water on its surface.[3][4]

A potentially habitable planet implies a terrestrial planet within the circumstellar habitable zone and with conditions roughly comparable to those of Earth (i.e. an Earth analog) and thus potentially favourable to Earth-like life.[citation needed] However, the question of what makes a planet habitable is much more complex than having a planet located at the right distance from its host star so that water can be liquid on its surface: various geophysical and geodynamical aspects, the radiation, and the host star’s plasma environment can influence the evolution of planets and life, if it originated.[2]

A 2015 review concluded that the exoplanets Kepler-62f, Kepler-186f and Kepler-442b were likely the best candidates for being potentially habitable.[8] These are at a distance of 1,200, 490 and 1,120 light-years away, respectively. Of these, Kepler-186f is similar in size to Earth with a 1.2-Earth-radius measure and it is located towards the outer edge of the habitable zone around its red dwarf.

This is a list of the exoplanets that are more likely to have a rocky composition (which according to current research[9][10] requires a radius of less than 1.6 R⊕ and a mass less than 6 M⊕) and maintain surface liquid water (i.e. between 0.5 and 1.5 R⊕ and between 0.1 and 5 M⊕, and orbiting within the conservative habitable zone). Note that this does not ensure habitability, and that * represents an unconfirmed planet or planet candidate. Earth is included for comparison.

This is a list of the exoplanets that are less likely to have a rocky composition or maintain surface liquid water (i.e. 0.5 < planet's radius ≤ 1.5 Earth radii or 0.1 < planet's minimum mass ≤ 10 Earth masses, or the planet is orbiting within the optimistic habitable zone). Note that this does not ensure habitability, and that * represents an unconfirmed planet or planet candidate.

HD 85512 b was initially estimated to be potentially habitable,[33][34] but updated models for the boundaries of the habitable zone placed the planet interior to the HZ,[35][36] and it is now considered non-habitable.[13]Kepler-69c has gone through a similar process; though initially estimated to be potentially habitable,[37] it was quickly realized that the planet is more likely to be similar to Venus,[38] and is thus no longer considered habitable.[13]

Similarly, Tau Ceti f was initially considered potentially habitable,[39] but the improved model of the circumstellar habitable zone places the planet exterior to the outer limits of habitability, so it is now considered non-habitable.[13]

KOI-1686.01 was also considered a potentially habitable exoplanet after its detection in 2011, until proven a false positive by NASA in 2015.[40]

1.
Exoplanets
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An exoplanet or extrasolar planet is a planet that orbits a star other than the Sun. The first scientific detection of an exoplanet was in 1988, HARPS has discovered about a hundred exoplanets while the Kepler space telescope has found more than two thousand. Kepler has also detected a few thousand candidate planets, of which about 11% may be false positives, on average, there is at least one planet per star, with a percentage having multiple planets. About 1 in 5 Sun-like stars have an Earth-sized planet in the habitable zone, the least massive planet known is Draugr, which is about twice the mass of the Moon. There are planets that are so near to their star that they take only a few hours to orbit, some are so far out that it is difficult to tell whether they are gravitationally bound to the star. Almost all of the planets detected so far are within the Milky Way, the nearest exoplanet is Proxima Centauri b, located 4.2 light-years from Earth and orbiting Proxima Centauri, the closest star to the Sun. The discovery of exoplanets has intensified interest in the search for extraterrestrial life, there is special interest in planets that orbit in a stars habitable zone, where it is possible for liquid water, a prerequisite for life on Earth, to exist on the surface. The study of planetary habitability also considers a range of other factors in determining the suitability of a planet for hosting life. The rogue planets in the Milky Way possibly number in the billions, the convention for designating exoplanets is an extension of the system used for designating multiple-star systems as adopted by the International Astronomical Union. For exoplanets orbiting a star, the designation is normally formed by taking the name or, more commonly, designation of its parent star. The first planet discovered in a system is given the designation b, if several planets in the same system are discovered at the same time, the closest one to the star gets the next letter, followed by the other planets in order of orbital size. A provisional IAU-sanctioned standard exists to accommodate the designation of circumbinary planets, a limited number of exoplanets have IAU-sanctioned proper names. Various detection claims made in the century were rejected by astronomers. The first scientific detection of an exoplanet began in 1988, However, the first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a star was made in 1995. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method, in the eighteenth century the same possibility was mentioned by Isaac Newton in the General Scholium that concludes his Principia. Claims of exoplanet detections have been made since the nineteenth century, some of the earliest involve the binary star 70 Ophiuchi. In 1855 William Stephen Jacob at the East India Companys Madras Observatory reported that orbital anomalies made it highly probable that there was a body in this system

2.
University of Puerto Rico at Arecibo
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The University of Puerto Rico at Arecibo is a state university located in the city of Arecibo, Puerto Rico, and part of the eleven campuses that compose the University of Puerto Rico system. UPR-Arecibo is known from its previous names Colegio Regional de Arecibo and Colegio Universitario Tecnológico de Arecibo and its acronyms CRA and it is accredited by the Middle States Association of Colleges and Schools. In addition, students in UPRAs Baccalaureate Program in Elementary Education highlighted by obtaining excellent scores on teacher certification exams of the Puerto Rico Department of Education, students,3,693 Faculty,257 Administrative personnel,288 Roberto Cortés, weather anchor at Telemundo Puerto Rico. Ricardo Torres, sports anchor at Telemundo Puerto Rico, eliezer Ramos, news reporter at WAPA-TV. Saudi Rivera, gossip analyst at Telemundo Puerto Rico, nelson Ruiz, producer of Mira Quien Baila and Nuestra Belleza Latina. Nuria Sebazco, news reporter at Telemundo Puerto Rico, jessica Serrano, gossip analyst at Telemundo Puerto Rico. Suheill Michelle Urdaz Montano, radio reporter at SuperK106, normando Valentín, news reporter at WAPA-TV The University of Puerto Rico at Arecibo has two fraternities, members of the Inter-Fraternity Council of Puerto Rico. Phi Omega Sigma Phi Sigma Alpha Association of the University of Puerto Rico Alumni and Friends Abroad University of Puerto Rico at Arecibo

3.
Planetary habitability
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Planetary habitability is the measure of a planets or a natural satellites potential to have habitable environments hospitable to life. Habitable environments do not need to contain life, Life may develop directly on a planet or satellite or be transferred to it from another body, a hypothetical process known as panspermia. Research and theory in this regard is a component of planetary science, in determining the habitability potential of a body, studies focus on its bulk composition, orbital properties, atmosphere, and potential chemical interactions. Stellar characteristics of importance include mass and luminosity, stable variability, the idea that planets beyond Earth might host life is an ancient one, though historically it was framed by philosophy as much as physical science. The late 20th century saw two breakthroughs in the field, the discovery of extrasolar planets, beginning in the early 1990s and accelerating thereafter, has provided further information for the study of possible extraterrestrial life. These findings confirm that the Sun is not unique among stars in hosting planets, the chemistry of life may have begun shortly after the Big Bang,13.8 billion years ago, during a habitable epoch when the Universe was only 10–17 million years old. According to the hypothesis, microscopic life—distributed by meteoroids, asteroids. Nonetheless, Earth is the place in the Universe known to harbor life. 11 billion of these planets may be orbiting Sun-like stars. The nearest such planet may be 12 light-years away, according to the scientists, an understanding of planetary habitability begins with the host star. Under the auspices of SETIs Project Phoenix, scientists Margaret Turnbull and Jill Tarter developed the HabCat in 2002. According to research published in August 2015, very large galaxies may be favorable to the formation and development of habitable planets than smaller galaxies. The spectral class of a star indicates its photospheric temperature, which correlates to overall mass, the appropriate spectral range for HabStars is considered to be late F or G, to mid-K. This corresponds to temperatures of a more than 7,000 K down to a little more than 4,000 K, the Sun. This spectral range probably accounts for between 5% and 10% of stars in the local Milky Way galaxy, middle-class stars of this sort have a number of characteristics considered important to planetary habitability, They live at least a few billion years, allowing life a chance to evolve. More luminous main-sequence stars of the O, B, and A classes usually live less than a billion years and they emit enough high-frequency ultraviolet radiation to trigger important atmospheric dynamics such as ozone formation, but not so much that ionisation destroys incipient life. Liquid water may exist on the surface of planets orbiting them at a distance that does not induce tidal locking, k-type stars may be able to support life far longer than the Sun. Gliese 581 c, a super-Earth, has been found orbiting in the zone of a red dwarf

4.
Geophysics
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Although geophysics was only recognized as a separate discipline in the 19th century, its origins date back to ancient times. The first magnetic compasses were made from lodestones, while more modern magnetic compasses played an important role in the history of navigation, the first seismic instrument was built in 132 BC. Geophysics is applied to societal needs, such as resources, mitigation of natural hazards. Geophysics is a highly interdisciplinary subject, and geophysicists contribute to area of the Earth sciences. To provide an idea of what constitutes geophysics, this section describes phenomena that are studied in physics and how they relate to the Earth. The gravitational pull of the Moon and Sun give rise to two high tides and two low tides every lunar day, or every 24 hours and 50 minutes, therefore, there is a gap of 12 hours and 25 minutes between every high tide and between every low tide. Gravitational forces make rocks press down on rocks, increasing their density as the depth increases. Measurements of gravitational acceleration and gravitational potential at the Earths surface, the surface gravitational field provides information on the dynamics of tectonic plates. The geopotential surface called the geoid is one definition of the shape of the Earth, the geoid would be the global mean sea level if the oceans were in equilibrium and could be extended through the continents. The Earth is cooling, and the heat flow generates the Earths magnetic field through the geodynamo. The main sources of heat are the heat and radioactivity. Some heat is carried up from the bottom of the mantle by mantle plumes, the heat flow at the Earths surface is about 4.2 ×1013 W, and it is a potential source of geothermal energy. Seismic waves are vibrations that travel through the Earths interior or along its surface, the entire Earth can also oscillate in forms that are called normal modes or free oscillations of the Earth. Ground motions from waves or normal modes are measured using seismographs, if the waves come from a localized source such as an earthquake or explosion, measurements at more than one location can be used to locate the source. The locations of earthquakes provide information on plate tectonics and mantle convection, measurements of seismic waves are a source of information on the region that the waves travel through. If the density or composition of the rock changes suddenly, some waves are reflected, reflections can provide information on near-surface structure. Changes in the direction, called refraction, can be used to infer the deep structure of the Earth. Earthquakes pose a risk to humans, understanding their mechanisms, which depend on the type of earthquake, can lead to better estimates of earthquake risk and improvements in earthquake engineering

5.
Geodynamics
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Geodynamics is a subfield of geophysics dealing with dynamics of the Earth. It also attempts to probe the internal activity by measuring magnetic fields, gravity, methods of geodynamics are also applied to exploration of other planets. Geodynamics is generally concerned with processes that move throughout the Earth. In the Earth’s interior, movement happens when rocks melt or deform and this deformation may be brittle, elastic, or plastic, depending on the magnitude of the stress and the material’s physical properties, especially the stress relaxation time scale. Rocks are structurally and compositionally heterogeneous and are subjected to variable stresses, when working with geological timescales and lengths, it is convenient to use the continuous medium approximation and equilibrium stress fields to consider the average response to average stress. Experts in geodynamics commonly use data from geodetic GPS, InSAR, rocks and other geological materials experience strain according three distinct modes, elastic, plastic, and brittle depending on the properties of the material and the magnitude of the stress field. Stress is defined as the force per unit area exerted on each part of the rock. Pressure is the part of stress changes the volume of a solid. If there is no shear, the fluid is in hydrostatic equilibrium, since, over long periods, rocks readily deform under pressure, the Earth is in hydrostatic equilibrium to a good approximation. The pressure on rock depends only on the weight of the rock above, and this depends on gravity, in a body like the Moon, the density is almost constant, so a pressure profile is readily calculated. In the Earth, the compression of rocks with depth is significant, elastic deformation is always reversible, which means that if the stress field associated with elastic deformation is removed, the material will return to its previous state. Materials only behave elastically when the arrangement along the axis being considered of material components remains unchanged. This means that the magnitude of the stress cannot exceed the strength of a material. If stress exceeds the strength of a material, bonds begin to break. During ductile deformation, this process of atomic rearrangement redistributes stress, examples include bending of the lithosphere under volcanic islands or sedimentary basins, and bending at oceanic trenches. Ductile deformation happens when transport processes such as diffusion and advection that rely on chemical bonds to be broken, when strain localizes faster than these relaxation processes can redistribute it, brittle deformation occurs. In other words, any fracture, however small, tends to focus strain at its leading edge, in general, the mode of deformation is controlled not only by the amount of stress, but also by the distribution of strain and strain associated features. Structural geologists study the results of deformation, using observations of rock, especially the mode, structural geology is an important complement to geodynamics because it provides the most direct source of data about the movements of the Earth

6.
Plasma (physics)
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Plasma is one of the four fundamental states of matter, the others being solid, liquid, and gas. Yet unlike these three states of matter, plasma does not naturally exist on the Earth under normal surface conditions, the term was first introduced by chemist Irving Langmuir in the 1920s. However, true plasma production is from the separation of these ions and electrons that produces an electric field. Based on the environmental temperature and density either partially ionised or fully ionised forms of plasma may be produced. The positive charge in ions is achieved by stripping away electrons from atomic nuclei, the number of electrons removed is related to either the increase in temperature or the local density of other ionised matter. Plasma may be the most abundant form of matter in the universe, although this is currently tentative based on the existence. Plasma is mostly associated with the Sun and stars, extending to the rarefied intracluster medium, Plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879. The nature of the Crookes tube cathode ray matter was identified by British physicist Sir J. J. The term plasma was coined by Irving Langmuir in 1928, perhaps because the glowing discharge molds itself to the shape of the Crookes tube and we shall use the name plasma to describe this region containing balanced charges of ions and electrons. Plasma is a neutral medium of unbound positive and negative particles. Although these particles are unbound, they are not ‘free’ in the sense of not experiencing forces, in turn this governs collective behavior with many degrees of variation. The average number of particles in the Debye sphere is given by the plasma parameter, bulk interactions, The Debye screening length is short compared to the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, when this criterion is satisfied, the plasma is quasineutral. Plasma frequency, The electron plasma frequency is compared to the electron-neutral collision frequency. When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics, for plasma to exist, ionization is necessary. The term plasma density by itself refers to the electron density, that is. The degree of ionization of a plasma is the proportion of atoms that have lost or gained electrons, even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma. The degree of ionization, α, is defined as α = n i n i + n n, where n i is the number density of ions and n n is the number density of neutral atoms

7.
Habitable zone
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The bounds of the CHZ are based on Earths position in the Solar System and the amount of radiant energy it receives from the Sun. Since the concept was first presented in 1953, many stars have been confirmed to possess a CHZ planet, most such planets, being super-Earths or gas giants, are more massive than Earth, because such planets are easier to detect. 11 billion of these may be orbiting Sun-like stars, proxima Centauri b, located about 4.2 light-years from Earth in the constellation of Centaurus, is the nearest known exoplanet, and is orbiting in the habitable zone of its star. The CHZ is also of particular interest to the field of habitability of natural satellites. In subsequent decades, the CHZ concept began to be challenged as a criterion for life. Since the discovery of evidence for liquid water, substantial quantities of it are now thought to occur outside the circumstellar habitable zone. Sustained by other sources, such as tidal heating or radioactive decay or pressurized by non-atmospheric means, liquid water may be found even on rogue planets. In addition, other circumstellar zones, where non-water solvents favorable to life based on alternative biochemistries could exist in liquid form at the surface, have been proposed. In the same year, Harlow Shapley wrote Liquid Water Belt, both works stressed the importance of liquid water to life. The theory of habitable zones was further developed in 1964 by Stephen H, at the same time, science-fiction author Isaac Asimov introduced the concept of a circumstellar habitable zone to the general public through his various explorations of space colonization. The term Goldilocks zone emerged in the 1970s, referencing specifically a region around a star whose temperature is just right for water to be present in the liquid phase. In 1993, astronomer James Kasting introduced the term circumstellar habitable zone to refer more precisely to the then known as the habitable zone. Whether a body is in the habitable zone of its host star is dependent on the radius of the planets orbit, the mass of the body itself. The outer edge of the HZ is the distance from the star where adding more carbon dioxide to the atmosphere fails to keep the surface of the planet above the freezing point. Estimates for the zone within the Solar System range from 0.5 to 3.0 astronomical units. Numerous planetary mass objects orbit within, or close to, this range, however their atmospheric conditions vary substantially. The entire orbits of the Moon, Mars, and numerous asteroids also lie within various estimates of the habitable zone, only at Mars lowest elevations is atmospheric pressure and temperature sufficient for water to, if present, exist in liquid form for short periods. At Hellas Basin, for example, atmospheric pressures can reach 1,115 Pa, despite indirect evidence in the form of seasonal flows on warm Martian slopes, no confirmation has been made of the presence of liquid water there

8.
Astronomy
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Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets, while the phenomena include supernovae explosions, gamma ray bursts, more generally, all astronomical phenomena that originate outside Earths atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole, Astronomy is the oldest of the natural sciences. The early civilizations in recorded history, such as the Babylonians, Greeks, Indians, Egyptians, Nubians, Iranians, Chinese, during the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the results and observations being used to confirm theoretical results. Astronomy is one of the few sciences where amateurs can play an active role, especially in the discovery. Amateur astronomers have made and contributed to many important astronomical discoveries, Astronomy means law of the stars. Astronomy should not be confused with astrology, the system which claims that human affairs are correlated with the positions of celestial objects. Although the two share a common origin, they are now entirely distinct. Generally, either the term astronomy or astrophysics may be used to refer to this subject, however, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Few fields, such as astrometry, are purely astronomy rather than also astrophysics, some titles of the leading scientific journals in this field includeThe Astronomical Journal, The Astrophysical Journal and Astronomy and Astrophysics. In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye, in some locations, early cultures assembled massive artifacts that possibly had some astronomical purpose. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye, most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon, the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the model of the Universe, or the Ptolemaic system. The Babylonians discovered that lunar eclipses recurred in a cycle known as a saros

9.
Astrobiology
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Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe, extraterrestrial life and life on Earth. Astrobiology addresses the question of whether life exists beyond Earth, the origin and early evolution of life is an inseparable part of the discipline of astrobiology. Although speculation is entertained to give context, astrobiology concerns itself primarily with hypotheses that fit firmly into existing scientific theories. The chemistry of life may have begun shortly after the Big Bang,13.8 billion years ago, according to the panspermia hypothesis, microscopic life—distributed by meteoroids, asteroids and other small Solar System bodies—may exist throughout the universe. According to research published in August 2015, very large galaxies may be favorable to the creation. Nonetheless, Earth is the place in the universe humans know to harbor life. The search for evidence of habitability, taphonomy, and organic molecules on the planet Mars is now a primary NASA and ESA objective. Astrobiology is etymologically derived from the Greek ἄστρον, astron, constellation, star, βίος, bios, life, the synonyms of astrobiology are diverse, however, the synonyms were structured in relation to the most important sciences implied in its development, astronomy and biology. A close synonym is exobiology from the Greek Έξω, external, Βίος, bios, life, the term exobiology was coined by molecular biologist Joshua Lederberg. Another term used in the past is xenobiology, a used in 1954 by science fiction writer Robert Heinlein in his work The Star Beast. The term xenobiology is now used in a more specialized sense, to mean biology based on foreign chemistry, since alternate chemistry analogs to some life-processes have been created in the laboratory, xenobiology is now considered as an extant subject. While it is an emerging and developing field, the question of whether life exists elsewhere in the universe is a verifiable hypothesis, though once considered outside the mainstream of scientific inquiry, astrobiology has become a formalized field of study. Planetary scientist David Grinspoon calls astrobiology a field of philosophy, grounding speculation on the unknown. NASAs interest in exobiology first began with the development of the U. S, in 1959, NASA funded its first exobiology project, and in 1960, NASA founded an Exobiology Program, which is now one of four main elements of NASAs current Astrobiology Program. NASAs Viking missions to Mars, launched in 1976, included three biology experiments designed to look for metabolism of present life on Mars, a particular focus of current astrobiology research is the search for life on Mars due to its proximity to Earth and geological history. Missions specifically designed to search for current life on Mars were the Viking program, the Viking results were inconclusive, and Beagle 2 failed minutes after landing. In late 2008, the Phoenix lander probed the environment for past and present planetary habitability of microbial life on Mars, in November 2011, NASA launched the Mars Science Laboratory mission carrying the Curiosity rover, which landed on Mars at Gale Crater in August 2012. The Curiosity rover is currently probing the environment for past and present planetary habitability of microbial life on Mars, the European Space Agency is currently collaborating with the Russian Federal Space Agency and developing the ExoMars astrobiology rover, which is to be launched in 2018

10.
Star
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It is primarily present in steroid-producing cells, including theca cells and luteal cells in the ovary, Leydig cells in the testis and cell types in the adrenal cortex. The aqueous phase between two membranes cannot be crossed by the lipophilic cholesterol, unless certain proteins assist in this process. It is now clear that this process is mediated by the action of StAR. The mechanism by which StAR causes cholesterol movement remains unclear as it appears to act from the outside of the mitochondria, some involve StAR transferring cholesterol itself like a shuttle. Another notion is that it causes cholesterol to be kicked out of the membrane to the inner. StAR may also promote the formation of contact sites between the outer and inner mitochondrial membranes to allow cholesterol influx, another suggests that StAR acts in conjunction with PBR, causing the movement of Cl− out of the mitochondria to facilitate contact site formation. However, evidence for an interaction between StAR and PBR remains elusive, in humans, the gene for StAR is located on chromosome 8p11.2 and the protein has 285 amino acids. The signal sequence of StAR that targets it to the mitochondria is clipped off in two steps with import into the mitochondria, phosphorylation at the serine at position 195 increases its activity. The domain of StAR important for promoting cholesterol transfer is the StAR-related transfer domain, StAR is the prototypic member of the START domain family of proteins and is thus also known as STARD1 for START domain-containing protein 1. It is hypothesized that the START domain forms a pocket in StAR that binds single cholesterol molecules for delivery to P450scc, the closest homolog to StAR is MLN64. Together they comprise the StarD1/D3 subfamily of START domain-containing proteins, StAR is a mitochondrial protein that is rapidly synthesized in response to stimulation of the cell to produce steroid. Hormones that stimulate its production depend on the type and include luteinizing hormone, ACTH. At the cellular level, StAR is synthesized typically in response to activation of the second messenger system. StAR has thus far found in all tissues that can produce steroids, including the adrenal cortex, the gonads, the brain. One known exception is the human placenta, mutations in the gene for StAR cause lipoid congenital adrenal hyperplasia, in which patients produce little steroid and can die shortly after birth. Mutations that less severely affect the function of StAR result in nonclassic lipoid CAH or familial glucocorticoid deficiency type 3, all known mutations disrupt StAR function by altering its START domain. In the case of StAR mutation, the phenotype does not present until birth since human placental steroidogenesis is independent of StAR. At the cellular level, the lack of StAR results in an accumulation of lipid within cells

11.
Planet
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of mass based on where or what they orbit. The planets were thought by Ptolemy to orbit Earth in deferent, at about the same time, by careful analysis of pre-telescopic observation data collected by Tycho Brahe, Johannes Kepler found the planets orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the planets share characteristics such as volcanism, hurricanes, tectonics. Planets are generally divided into two types, large low-density giant planets, and smaller rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System, in order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, several thousands of planets around other stars have been discovered in the Milky Way. e. in the habitable zone. On December 20,2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way, around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone. The idea of planets has evolved over its history, from the lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include not only in the Solar System. The ambiguities inherent in defining planets have led to much scientific controversy, the five classical planets, being visible to the naked eye, have been known since ancient times and have had a significant impact on mythology, religious cosmology, and ancient astronomy. In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the fixed stars, ancient Greeks called these lights πλάνητες ἀστέρες or simply πλανῆται, from which todays word planet was derived. In ancient Greece, China, Babylon, and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the planets circled Earth. The first civilization known to have a theory of the planets were the Babylonians

12.
Terrestrial planet
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A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the planets are the inner planets closest to the Sun, i. e. Mercury, Venus, Earth. The terms terrestrial planet and telluric planet are derived from Latin words for Earth, as these planets are, in terms of composition, Earth-like. All terrestrial planets may have the basic type of structure, such as a central metallic core, mostly iron. The Moon is similar, but has a smaller iron core. Io and Europa are also satellites that have internal structures similar to that of terrestrial planets, terrestrial planets can have canyons, craters, mountains, volcanoes, and other surface structures, depending on the presence of water and tectonic activity. The Solar System has four planets, Mercury, Venus, Earth. Only one terrestrial planet, Earth, is known to have an active hydrosphere, during the formation of the Solar System, there were probably many more terrestrial planetesimals, but most merged with or were ejected by the four terrestrial planets. The Earths Moon has a density of 3.4 g·cm−3 and Jupiters satellites, Io,3.528 and Europa,3.013 g·cm−3, the uncompressed density of a terrestrial planet is the average density its materials would have at zero pressure. A greater uncompressed density indicates greater metal content, uncompressed density differs from the true average density because compression within planet cores increases their density, the average density depends on planet size as well as composition. The uncompressed density of terrestrial planets trends towards lower values as the distance from the Sun increases, the rocky minor planet Vesta orbiting outside of Mars is less dense than Mars still, at 3.4 g·cm−3. It is unknown whether extrasolar terrestrial planets in general will also follow this trend, most of the planets discovered outside the Solar System are giant planets, because they are more easily detectable. But since 2005, hundreds of terrestrial extrasolar planets have been found. Most of these are super-Earths, i. e. planets with masses between Earths and Neptunes, super-Earths may be gas planets or terrestrial, depending on their mass and other parameters. During the early 1990s, the first extrasolar planets were discovered orbiting the pulsar PSR B1257+12, with masses of 0.02,4.3 and it was later found to be a gas giant. In 2005, the first planets around stars that may be terrestrial were found, Gliese 876 d, has a mass 7 to 9 times that of Earth. It orbits the red dwarf Gliese 876,15 light years from Earth, oGLE-2005-BLG-390Lb, about 5.5 times the mass of Earth, orbits a star about 21,000 light years away in the constellation Scorpius. From 2007 to 2010, three potential terrestrial planets were orbiting the red dwarf Gliese 581

13.
Earth analog
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An Earth analog is a planet or moon with environmental conditions similar to those found on the planet Earth. The possibility is of particular interest to astronomers under reasoning that the more similar a planet is to Earth, as such, it has long been speculated and the subject expressed in science, philosophy, science fiction and popular culture. Advocates of space colonization have long sought an Earth analog as a home, while advocates for space. Before the scientific search for and study of planets, the possibility was argued through philosophy. The mediocrity principle suggests that planets like Earth should be common in the universe, the thousands of exoplanetary star systems discovered so far are profoundly different from our solar system, supporting the Rare Earth hypothesis. Philosophers have pointed out that the size of the universe is such that a planet must exist somewhere. In the future, technology may be used by humans to produce an Earth analog by terraforming. The multiverse theory suggests that an Earth analog could exist in another universe or even be another version of the Earth itself in a parallel universe,11 billion of these estimated planets may be orbiting Sun-like stars. The nearest such planet may be 12 light-years away, scientific findings since the 1990s have greatly influenced the scope of the fields of astrobiology, models of planetary habitability and the search for extraterrestrial intelligence. NASA and the SETI Institute have proposed categorising the increasing number of planets found using a measure called the Earth Similarity Index based on mass, radius and temperature. According to this measure, as of 23 July 2015, the confirmed planet currently thought to be most similar to Earth on mass, radius, scientists estimate that there may be billions of Earth-size planets within the Milky Way galaxy alone. Around 400 BC, Philolaus proposed that there existed a Counter-Earth and these theories were advanced by Giovanni Schiaparelli, Percival Lowell and others. As such Mars in fiction portrayed the red planet as similar to Earth but with a desert like landscape, images and data from the Mariner and Viking space probes, however, revealed the planet as a barren cratered world. However, with continuing discoveries, other Earth comparisons remained, for example, the Mars Ocean Hypothesis had its origins in the Viking missions and was popularised during the 1980s. With the possibility of past water, there was the possibility that life could have begun on Mars, Venus in fiction was often portrayed as having similarities to Earth and many speculated about Venusian civilization. From 2004, Cassini–Huygens began to reveal Saturns moon Titan to be one of the most Earth-like worlds outside of the habitable zone. Though having a different chemical makeup, discoveries such as the confirmation of Titanian lakes, rivers and fluvial processes in 2007. Further observations including weather phenomena has aided the understanding of processes that may operate on Earth-like planets

14.
Kepler (spacecraft)
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Kepler is a space observatory launched by NASA to discover Earth-size planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched on March 7,2009 and these data are transmitted to Earth, then analyzed to detect periodic dimming caused by exoplanets that cross in front of their host star. Kepler is part of NASAs Discovery Program of relatively low-cost, focused primary science missions, the telescopes construction and initial operation were managed by NASAs Jet Propulsion Laboratory, with Ball Aerospace responsible for developing the Kepler flight system. The Ames Research Center is responsible for the system development, mission operations since December 2009. The initial planned lifetime was 3.5 years, but greater-than-expected noise in the data, then, on May 11,2013, a second reaction wheel failed, disabling the collection of science data and threatening the continuation of the mission. On August 15,2013, NASA announced that they had given up trying to fix the two failed reaction wheels and this meant the current mission needed to be modified, but it did not necessarily mean the end of planet hunting. NASA had asked the space science community to propose alternative mission plans potentially including an exoplanet search, on November 18,2013, the K2 Second Light proposal was reported. This would include utilizing the disabled Kepler in a way that could detect habitable planets around smaller, dimmer red dwarfs, on May 16,2014, NASA announced the approval of the K2 extension. As of January 2015, Kepler and its follow-up observations had found 1,013 confirmed exoplanets in about 440 star systems, four planets have been confirmed through Keplers K2 mission. It is estimated that 11 billion of these planets may be orbiting Sun-like stars, the nearest such planet may be 3.7 parsecs away, according to the scientists. On January 6,2015, NASA announced the 1, 000th confirmed exoplanet discovered by the Kepler Space Telescope, on May 10,2016, NASA verified 1,284 new exoplanets found by Kepler, the single largest finding of planets to date. Since 1988, over 3,000 exoplanets have been confirmed by all detection methods, the spacecraft has a 115 deg2 field of view, roughly equivalent to the size of ones fist held at arms length. Of this,105 deg2 is of quality, with less than 11% vignetting. The photometer has a focus to provide excellent photometry, rather than sharp images. The mission goal is a combined differential photometric precision of 20 ppm for a m=12 Sun-like star for a 6. 5-hour integration, an Earth-size planet transit produces a brightness change of 84 ppm and lasts for thirteen hours when it crosses the midline of the star. The array is cooled by heat pipes connected to an external radiator, the CCDs are read out every six seconds and co-added on board for 58.89 seconds for short cadence targets, and 1765.5 seconds for long cadence targets. Due to the bandwidth requirements for the former, these are limited in number to 512 compared to 170,000 for long cadence. However, even though at launch Kepler had the highest data rate of any NASA mission, therefore, the science team has pre-selected the relevant pixels associated with each star of interest, amounting to about 6 percent of the pixels

15.
Extrasolar planets
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An exoplanet or extrasolar planet is a planet that orbits a star other than the Sun. The first scientific detection of an exoplanet was in 1988, HARPS has discovered about a hundred exoplanets while the Kepler space telescope has found more than two thousand. Kepler has also detected a few thousand candidate planets, of which about 11% may be false positives, on average, there is at least one planet per star, with a percentage having multiple planets. About 1 in 5 Sun-like stars have an Earth-sized planet in the habitable zone, the least massive planet known is Draugr, which is about twice the mass of the Moon. There are planets that are so near to their star that they take only a few hours to orbit, some are so far out that it is difficult to tell whether they are gravitationally bound to the star. Almost all of the planets detected so far are within the Milky Way, the nearest exoplanet is Proxima Centauri b, located 4.2 light-years from Earth and orbiting Proxima Centauri, the closest star to the Sun. The discovery of exoplanets has intensified interest in the search for extraterrestrial life, there is special interest in planets that orbit in a stars habitable zone, where it is possible for liquid water, a prerequisite for life on Earth, to exist on the surface. The study of planetary habitability also considers a range of other factors in determining the suitability of a planet for hosting life. The rogue planets in the Milky Way possibly number in the billions, the convention for designating exoplanets is an extension of the system used for designating multiple-star systems as adopted by the International Astronomical Union. For exoplanets orbiting a star, the designation is normally formed by taking the name or, more commonly, designation of its parent star. The first planet discovered in a system is given the designation b, if several planets in the same system are discovered at the same time, the closest one to the star gets the next letter, followed by the other planets in order of orbital size. A provisional IAU-sanctioned standard exists to accommodate the designation of circumbinary planets, a limited number of exoplanets have IAU-sanctioned proper names. Various detection claims made in the century were rejected by astronomers. The first scientific detection of an exoplanet began in 1988, However, the first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a star was made in 1995. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method, in the eighteenth century the same possibility was mentioned by Isaac Newton in the General Scholium that concludes his Principia. Claims of exoplanet detections have been made since the nineteenth century, some of the earliest involve the binary star 70 Ophiuchi. In 1855 William Stephen Jacob at the East India Companys Madras Observatory reported that orbital anomalies made it highly probable that there was a body in this system

16.
Solar analog
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Solar-type star, solar analogs, and solar twins are stars that are particularly similar to the Sun. The stellar classification is a hierarchy with solar twin being most like the Sun followed by solar analog, Observations of these stars are important for understanding better the properties of the Sun in relation to other stars and the habitability of planets. Defining the three categories by their similarity to the Sun reflects the evolution of astronomical observational techniques, originally, solar-type was the closest that similarity to the Sun could be defined. Later still, continued improvements in precision allowed for the creation of a category for near-perfect matches. Similarity to the Sun allows for checking derived quantities—such as temperature, which is derived from the color index—against the Sun, for stars that are not similar to the Sun, this cross-checking cannot be done. These stars are similar to the Sun. They are main-sequence stars with a B−V color between 0.48 and 0.80, the Sun having a B−V color of 0.65. Alternatively, a based on spectral type can be used, such as F8V through K2V. This definition fits approximately 10% of stars, so a list of stars would be quite extensive. Mamajek & Hillenbrand have estimated the ages for the 108 solar-type main-sequence stars within 52 light-years of the Sun based on their chromospheric activity. An exact solar twin would be a G2V star with a 5, 778K temperature, be 4.6 billion years old, with the correct metallicity, Stars with an age of 4.6 billion years are at the most stable state. Proper metallicity and size are very important to low luminosity variation. The Sun is listed for comparison, highlighted boxes are out of range for a solar twin, but the star may have been noted as solar twin in the past. Some other stars are mentioned as solar-twin candidates such as, Beta Canum Venaticorum. 16 Cygni B is sometimes noted as twin, but is part of a star system and is very old for a solar twin at over 9 Gyr. Another way of defining solar twin is as a habstar — a star with qualities believed to be hospitable to an Earth-like planet. Qualities considered include variability, mass, age, metallicity, at least 3 billion years old On the main sequence Non-variable Capable of harboring terrestrial planets Support a dynamically stable habitable zone No stellar companion star. The requirement that the star remain on the sequence for at least 3 Ga sets an upper limit of approximately 1.5 solar masses

17.
Red dwarf
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In May 2015, it was announced that Series XI and XII would film back-to-back later in 2015 and would air exclusively on the Dave channel in 2016 and 2017. The first episode of Red Dwarf XI aired at 9 p. m. on Thursday 22 September 2016 on Dave and has been available via streaming service UKTV Play from Thursday 15 September 2016, the series was created by Rob Grant and Doug Naylor. Despite the pastiche of science fiction used as a backdrop, Red Dwarf is primarily a character-driven comedy, the main characters are Dave Lister, the last known human alive, and Arnold Rimmer, a hologram of Listers dead bunkmate. The series attracted its highest ratings, of more than eight million viewers, the series was revived after a ten-year break, when digital channel Dave screened a three-episode production, titled Red Dwarf, Back to Earth, in April 2009 during the Easter weekend. This was followed by Series X, consisting of six episodes, the show has been critically acclaimed, and has a Metacritic score of 84/100. Series XI was voted Best Returning TV Sitcom and Comedy of the Year for 2016 by readers for the British Comedy Guide. The show was based on Dave Hollins, Space Cadet, a series of five sketches that aired in the BBC Radio 4 series Son of Cliché, produced by Rob Grant and Doug Naylor in 1984. The sketches recounted the adventures of Dave Hollins, a space traveller who is marooned in space far from earth. His only steady companion is the computer Hab, Grant and Naylor chose to use the Dave Hollins, Space Cadet sketches as a base for a television show after watching the 1974 film Dark Star. They changed some elements from the sketches, The 7 trillion year figure was first changed to 7 billion years and then to 3 million and the characters of Arnold Rimmer and the Cat were created. The name Dave Hollins was changed to Dave Lister when a player called Dave Hollins became well-known. One of the actors from Son of Cliché, Chris Barrie went on to portray Arnold Rimmer in the Red Dwarf TV series. Episodes of Dave Hollins can be found on the 2-disc Red Dwarf DVD sets starting with series 5 and ending with series 8. The main setting of the series is the eponymous mining spaceship Red Dwarf, which is 6 miles long,4 miles tall, following the accident, the ships computer Holly keeps Lister in stasis until the radiation levels return to normal – a process that takes three million years. Lister therefore emerges as the last human being in the universe – and his former bunkmate and immediate superior Arnold Judas Rimmer is resurrected by Holly as a hologram to keep Lister sane. During the second series, the encounter the service mechanoid Kryten. Initially, Kryten only appeared in one episode of two, but by the beginning of series three he had become a regular character. A complicated series of events leaves Kochanski stranded in the main universe

18.
Milky Way
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The Milky Way is the galaxy that contains our Solar System. The descriptive milky is derived from the appearance from Earth of the galaxy – a band of light seen in the night sky formed from stars that cannot be distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610, until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies, the Milky Way is a barred spiral galaxy with a diameter between 100,000 light-years and 180,000 light-years. The Milky Way is estimated to contain 100–400 billion stars, there are probably at least 100 billion planets in the Milky Way. The Solar System is located within the disk, about 26,000 light-years from the Galactic Center, on the edge of one of the spiral-shaped concentrations of gas. The stars in the inner ≈10,000 light-years form a bulge, the very center is marked by an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole. Stars and gases at a range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests much of the mass of the Milky Way does not emit or absorb electromagnetic radiation. This mass has been termed dark matter, the rotational period is about 240 million years at the position of the Sun. The Milky Way as a whole is moving at a velocity of approximately 600 km per second with respect to frames of reference. The oldest stars in the Milky Way are nearly as old as the Universe itself, the Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which is a component of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster. The Milky Way can be seen as a band of white light some 30 degrees wide arcing across the sky. Dark regions within the band, such as the Great Rift, the area of the sky obscured by the Milky Way is called the Zone of Avoidance. The Milky Way has a low surface brightness. Its visibility can be reduced by background light such as light pollution or stray light from the Moon. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be seen and it should be visible when the limiting magnitude is approximately +5.1 or better and shows a great deal of detail at +6.1

19.
Kepler-62f
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Kepler-62f is a super-Earth exoplanet orbiting within the habitable zone of the star Kepler-62, the outermost of five such planets discovered by NASAs Kepler spacecraft. It is located about 1,200 light-years from Earth in the constellation of Lyra, the exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. Kepler-62f may be a terrestrial or ocean-covered planet, it lies within the part of its host stars habitable zone. Kepler-62f is a super-Earth, an exoplanet with a radius and mass bigger than Earth and it has an equilibrium temperature of 208 K, close to that of Mars. It has a radius of 1.4 R⊕, placing it below the radius of ≥1.6 R⊕ where it would otherwise be a mini-Neptune with a volatile composition, due to its radius, it is likely a rocky planet. However, the mass isnt constrained yet, estimates place a limit of <35 M⊕. The true value is likely around 2.8 M⊕, assuming a rocky composition, the planet orbits a star named Kepler-62, orbited by a total of five planets. The star has a mass of 0.69 M☉ and a radius of 0.64 R☉ and it has a temperature of 4925 K and is 7 billion years old. In comparison, the Sun is 4.6 billion years old and has a temperature of 5778 K, the star is somewhat metal-poor, with a metallicity of −0.37, or 42% of the solar amount. Its luminosity is 21% that of the Sun, the stars apparent magnitude, or how bright it appears from Earths perspective, is 13.65. Therefore, it is too dim to be seen with the naked eye, Kepler-62f orbits its host star with an orbital period of 267.29 days at a distance of about 0.718 AU. It receives 41% of the amount of sunlight that Earth does from the Sun, given the planets age, irradiance and radius, a rocky composition with the addition of a possibly substantial amount of water is considered plausible. A modeling study indicates it is likely that a majority of planets in its size range are completely covered by ocean. If its density is the same as Earths, its mass would be 1.413 or 2.80 times Earths, the planet has the potential for hosting a moon according to a study of tidal effects on potentially habitable planets. The planet may be the only candidate which would avoid desiccation by irradiation from the host star at its current location. In order for Kepler-62f to sustain an Earth-like climate (with an average temperature of around 284–290 K, because it is the outermost planet, the effects of tidal evolution from the inner planets and the host star on Kepler-62f are not likely to have had significant outcomes over its lifetime. The axial tilt is likely to have been unchanged, and thus, K-type stars like Kepler-62 can live for approximately 20–40 billion years,2 to 4 times longer than the estimated lifetime of our Sun. The low stellar activity of orange dwarfs like Kepler-62, creates a relatively benign environment for planets orbiting in their habitable zones

20.
Kepler-186f
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Kepler-186f is an exoplanet orbiting the red dwarf Kepler-186, about 500 light-years from the Earth. It is the first planet with a similar to Earths to be discovered in the habitable zone of another star. NASAs Kepler spacecraft detected it using the method, along with four additional planets orbiting much closer to the star. Analysis of three years of data was required to find its signal, the results were presented initially at a conference on 19 March 2014 and some details were reported in the media at the time. The public announcement was on 17 April 2014, followed by publication in Science and this ratio was measured to be 0.021. This yields a planetary radius of 1. 11±0.14 times that of Earth, taking into account uncertainty in the stars diameter, thus, the planet is about 11% larger in radius than Earth, giving a volume about 1.37 times that of Earth. A very wide range of masses can be calculated by combining the radius with densities derived from the possible types of matter from which planets can be made. For example, it could be a terrestrial planet or a lower density ocean planet with a thick atmosphere. Red dwarfs emit a much stronger extreme ultraviolet flux when young than later in life, mass estimates range from 0.32 M⊕ for a pure water/ice composition to 3.77 M⊕ if made up entirely of iron. For a body with radius 1.11 R⊕, a similar to that of Earth yields a mass of 1.44 M⊕. The estimated equilibrium temperature for Kepler-186f, which is the temperature without an atmosphere, is said to be around 188 K. The planet orbits a star named Kepler-186, orbited by a total of five planets, the star has a mass of 0.54 M☉ and a radius of 0.52 R☉. It has a temperature of 4017 K and is about 4 billion years old, about 600 million years younger than the Sun, the stars apparent magnitude, or how bright it appears from Earths perspective, is 14.62. Therefore, it is too dim to be seen with the naked eye, Kepler-186f orbits its star with about 4% of the Suns luminosity with an orbital period of 129.9 days and an orbital radius of about 0.40 times that of Earths. The habitable zone for this system is estimated conservatively to extend over distances receiving from 88% to 25% of Earths illumination, Kepler-186f receives about 32%, placing it within the conservative zone but near the outer edge, similar to the position of Mars in our Solar System. Kepler-186fs location within the zone does not ensure it is habitable, this is also dependent on its atmospheric characteristics. The star hosts four other planets discovered so far, although Kepler-186 b, c, d, because of the very slow evolution of red dwarfs, the age of the Kepler-186 system was poorly constrained, although it is likely to be greater than a few billion years. Recent results have placed the age at around 4 billion years, the chance that it is tidally locked is approximately 50%

21.
Kepler-442b
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The planet was discovered by NASAs Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the confirmation of the exoplanet on 6 January 2015, Kepler-442b is a super-Earth, an exoplanet with a mass and radius bigger than that of Earth, but smaller than that of the ice giants Uranus and Neptune. It has a temperature of 233 K. It has a radius of 1.34 R⊕, because of its radius, it is likely to be a rocky planet with a solid surface. The mass of the exoplanet is estimated to be 2.34 M⊕, the surface gravity on Kepler-442b would be 30% stronger than that of Earth, assuming a rocky composition similar to that of Earth. The planet orbits a star named Kepler-442, the star has a mass of 0.61 M☉ and a radius of 0.60 R☉. It has a temperature of 4402 K and is around 2.9 billion years old, in comparison, the Sun is 4.6 billion years old and has a temperature of 5778 K. The star is somewhat metal-poor, with a metallicity of −0.37 and its luminosity is 11% that of the Sun. The stars apparent magnitude, or how bright it appears from Earths perspective, is 14.97, therefore, it is too dim to be seen with the naked eye. Kepler-442b orbits its host star with a period of 112.3 days. It receives about 70% of the sunlight that Earth receives from the Sun, the planet was announced as being located within the habitable zone of its star, a region where liquid water could exist on the surface of the planet. It was described as being one of the most Earth-like planets, in terms of size and temperature and it is outside of the zone where tidal forces from its host star would be enough to tidally lock it. K-type main-sequence stars are smaller than the Sun and live longer, despite these properties, the small M-type and K-type stars can pose a threat to life. Because of their high activity at the beginning of their lives. The duration of this period is linked to the size of the star. However, because of the uncertainty of the age of Kepler-442, it is likely it may have passed this stage, making Kepler-442b potentially more suitable for habitability. Because it is closer to its star than Earth is to the Sun and this is reflected on its orbital distance just outside of the point where the tidal interactions from its star would be strong enough to tidally locked. Kepler-442bs axial tilt is very small, in which case it would not have tilt-induced seasons as Earth

22.
Star type
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In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with absorption lines, each line indicates an ion of a certain chemical element, with the line strength indicating the abundance of that ion. The relative abundance of the different ions varies with the temperature of the photosphere, the spectral class of a star is a short code summarizing the ionization state, giving an objective measure of the photospheres temperature and density. Most stars are classified under the Morgan–Keenan system using the letters O, B, A, F, G, K, and M. Each letter class is subdivided using a numeric digit with 0 being hottest and 9 being coolest. The sequence has been expanded with classes for other stars and star-like objects that do not fit in the system, such as class D for white dwarfs. In the MK system, a luminosity class is added to the class using Roman numerals. This is based on the width of absorption lines in the stars spectrum. The full spectral class for the Sun is then G2V, indicating a main-sequence star with a temperature around 5,800 K, the conventional color description takes into account only the peak of the stellar spectrum. This means that the assignment of colors of the spectrum can be misleading. There are no green, indigo, or violet stars, likewise, the brown dwarfs do not literally appear brown. The modern classification system is known as the Morgan–Keenan classification, each star is assigned a spectral class from the older Harvard spectral classification and a luminosity class using Roman numerals as explained below, forming the stars spectral type. The spectral classes O through M, as well as more specialized classes discussed later, are subdivided by Arabic numerals. For example, A0 denotes the hottest stars in the A class, fractional numbers are allowed, for example, the star Mu Normae is classified as O9.7. The Sun is classified as G2, the conventional color descriptions are traditional in astronomy, and represent colors relative to the mean color of an A-class star, which is considered to be white. The apparent color descriptions are what the observer would see if trying to describe the stars under a dark sky without aid to the eye, or with binoculars. However, most stars in the sky, except the brightest ones, red supergiants are cooler and redder than dwarfs of the same spectral type, and stars with particular spectral features such as carbon stars may be far redder than any black body. O-, B-, and A-type stars are called early type

23.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun

24.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions

25.
Proxima Centauri
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Proxima Centauri or Alpha Centauri C is a red dwarf, a small low-mass star, about 4.25 light-years from the Sun in the constellation of Centaurus. It was discovered in 1915 by the Scottish astronomer Robert Innes, the Director of the Union Observatory in South Africa, with an apparent magnitude of 11.05, it is too faint to be seen with the naked eye. Proxima Centauri forms a component of the Alpha Centauri binary star system, currently with a separation of about 13000+300 −100 AU. Because of Proxima Centauris proximity to Earth, its diameter can be measured directly. It is about one-seventh the diameter of the Sun and it has a mass about an eighth of the Suns mass, and its average density is about 40 times that of the Sun. Although it has a low average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness because of magnetic activity. The stars magnetic field is created by convection throughout the body. In 2016, the European Southern Observatory announced the discovery of Proxima b and its estimated mass is at least 1.3 times that of the Earth. Previous searches for orbiting companions had ruled out the presence of brown dwarfs, in 1915, the Scottish astronomer Robert Innes, Director of the Union Observatory in Johannesburg, South Africa, discovered a star that had the same proper motion as Alpha Centauri. He suggested that it be named Proxima Centauri and it was also found to be the lowest-luminosity star known at the time. An equally accurate parallax determination of Proxima Centauri was made by American astronomer Harold L. Alden in 1928, in 1951, American astronomer Harlow Shapley announced that Proxima Centauri is a flare star. Examination of past photographic records showed that the star displayed an increase in magnitude on about 8% of the images. The proximity of the star allows for detailed observation of its flare activity, in 1980, the Einstein Observatory produced a detailed X-ray energy curve of a stellar flare on Proxima Centauri. Further observations of flare activity were made with the EXOSAT and ROSAT satellites, Proxima Centauri has since been the subject of study by most X-ray observatories, including XMM-Newton and Chandra. In 2016, the International Astronomical Union organized a Working Group on Star Names to catalogue, the WGSN approved the name Proxima Centauri for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names. Because of Proxima Centauris southern declination, it can only be viewed south of latitude 27° N, Red dwarfs such as Proxima Centauri are far too faint to be seen with the naked eye. Even from Alpha Centauri A or B, Proxima would only be seen as a fifth magnitude star, Proxima Centauri is a red dwarf, because it belongs to the main sequence on the Hertzsprung–Russell diagram and is of spectral class M6. M6 means that it falls in the end of M-type stars

26.
Gliese 667 Cc
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The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planets parent star. Gliese 667 Cc is a super-Earth, an exoplanet with a mass and radius greater than that of Earth and it is heavier than Earth with a minimum mass of about 3.7 Earth masses. The equilibrium temperature of Gliese 667 Cc is estimated to be 277.4 K and it is expected to have a radius of around 1.5 R⊕, based on its composition. The planet orbits a red dwarf star named Gliese 667 C, the star is part of a trinary star system, with Gliese 667 A and B both being more massive than the smaller companion. Gilese 667 C has a mass of 0.31 M☉ and it has a temperature of 3700 K, but its age is poorly constrained, estimates place it greater than 2 billion years old. In comparison, the Sun is 4.6 billion years old and has a temperature of 5778 K. This star is radiating only 1. 4% of the Suns luminosity from its outer atmosphere. It is known to have a system of two planets, claims have made for up to seven, but these may be in error due to failure to account for correlated noise in the radial velocity data. Since red dwarfs emit little light, the planets likely receive minimal amounts of ultraviolet radiation. Gliese 667 Cc is the confirmed planet out from Gliese 667 C. From its surface, the star would have a diameter of 1.24 degrees. The apparent magnitude of the star is 10.25, giving it an absolute magnitude of about 11.03. It is too dim to be seen from Earth with the naked eye, the orbit of Gliese 667Cc has a semi-major axis of 0.1251 astronomical units, making its year 28.155 Earth-days long. In fact, taking into account solely the visual luminosity. According to PHL, Gliese 667 Cc is the third most Earth-like exoplanet located in the habitable zone of its parent star. Its host star is a red dwarf, with about a third as much mass than the Sun does, as a result, stars like Gliese 667 C have the ability to live up to 100–150 billion years, 10–15 times longer than the Sun will live. The planet is tidally locked, with one side of its hemisphere permanently facing towards the star. However, between two intense areas, there would be a sliver of habitability – called the terminator line

27.
Gliese 667 C
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Gliese 667 is a triple-star system in the constellation of Scorpius lying at a distance of about 6.8 pc from Earth. All three of the stars have masses smaller than the Sun, there is a 12th magnitude star close to the other three, but it is not gravitationally bound to the system. To the naked eye, the system appears to be a faint star of magnitude 5.89. The system has a high proper motion, exceeding 1 second of arc per year. The two brightest stars in this system, GJ667 A and GJ667 B, are orbiting each other at an angular separation of 1.81 arcseconds with a high eccentricity of 0.58. At the estimated distance of this system, this is equivalent to a separation of about 12.6 AU. Their eccentric orbit brings the pair as close as about 5 AU to each other, or as distant as 20 AU, corresponding to an eccentricity of 0.6. This orbit takes approximately 42.15 years to complete and the plane is inclined at an angle of 128° to the line of sight from the Earth. The third star, GJ667 C, orbits the GJ667 AB pair at a separation of about 30. The largest star in the system, Gliese 667 A, is a K-type main-sequence star of stellar classification K3V and it has about 73% of the mass of the Sun and 76% of the Suns radius, but is radiating only around 12-13% of the luminosity of the Sun. The concentration of other than hydrogen and helium, what astronomers term the stars metallicity, is much lower than in the Sun with a relative abundance of around 26% solar. The apparent visual magnitude of this star is 6.29, like the primary, the secondary star Gliese 667 B is a K-type main-sequence star, although it has a slightly later stellar classification of K5V. This star has a mass of about 69% of the Sun, or 95% of the primarys mass, the secondarys apparent magnitude is 7.24, giving it an absolute magnitude of around 8.02. Gliese 667 C is the smallest star in the system, with only around 31% of the mass of the Sun and 42% of the Suns radius and it is a red dwarf with a stellar classification of M1.5. This star is radiating only 1. 4% of the Suns luminosity from its atmosphere at a relatively cool effective temperature of 3,700 K. This temperature is what gives it the red-hued glow that is a characteristic of M-type stars, the apparent magnitude of the star is 10.25, giving it an absolute magnitude of about 11.03. It is known to have a system of two planets, claims have made for up to seven but these may be in error due to failure to account for correlated noise in the radial velocity data. The red dwarf status of the star would allow any planets to receive minimal amounts of ultraviolet radiation, two extrasolar planets, Gliese 667 Cb and Gliese 667 Cc, have been confirmed orbiting Gliese 667 C by radial velocity measurements of GJ667

28.
Kepler-452b
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Kepler-452b is an exoplanet orbiting the Sun-like star Kepler-452 about 1,400 light-years from Earth in the constellation Cygnus. It was identified by the Kepler space telescope, and its discovery was announced by NASA on 23 July 2015 and it is the first potentially rocky super-Earth planet discovered orbiting within the habitable zone of a star very similar to the Sun. The planet is about 1,400 light-years away from the Solar System, at the speed of the New Horizons spacecraft, about 59,000 km/h, it would take approximately 26 million years to get there. Kepler-452b has a mass five times that of Earth, and its surface gravity is twice Earths. If it is a planet, it is most likely a super-Earth with many active volcanoes due to its higher mass. The clouds on the planet would be thick and misty, covering much of the surface as viewed from space, the planet takes 385 Earth days to orbit its star. Its radius is 50% bigger than Earths, and lies within the habitable zone of its parent star. It has a temperature of 265 K, a little warmer than Earth. The host star, Kepler-452, is a G-type star that is about the mass of the Sun, only 3. 7% more massive. It has a temperature of 5757 K, nearly the same as the Sun. The stars age is estimated to be about 6 billion years old, about 1.4 billion years older than the Sun, from the surface of Kepler-452b, its star would look almost identical to the Sun as viewed from the Earth. The stars apparent magnitude, or how bright it appears from Earths perspective, is 13.426, therefore, it is too dim to be seen with the naked eye. Kepler-452b orbits its host star with about 20% more of the Suns luminosity with a period of 385 days. It is not known if Kepler-452b is a planet but based on its small radius. It is not clear if Kepler-452b offers habitable environments and it orbits a G2V-type star, like the Sun, with nearly the same temperature and mass and 20% more luminous. However, the star is six years old, making it 1.4 billion years older than the Sun. At this point in its stars evolution, Kepler-452b is receiving 10% more energy from its parent star than Earth is currently receiving from the Sun, if Kepler-452b is a rocky planet, it may be subject to a runaway greenhouse effect similar to that seen on Venus. This in turn would be accompanied with the cycle being buffed in duration due to increased volcanic activity on Kepler-452b

29.
Kepler-452
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Kepler-452 is a G-type main-sequence star located about 1400 light-years away from Earth in the constellation of Cygnus. It has a temperature to that of the Sun. It is approximately six years old,1.5 billion years older than the Sun. Thus, Kepler-452 can be considered a twin, however its age pushes it more back towards the solar analog criteria. Prior to Kepler observation, Kepler-452 had the 2MASS catalogue number 2MASS 19440088+4416392, in the Kepler Input Catalog it has the designation of KIC8311864, and when it was found to have a transiting planet candidate it was given the Kepler object of interest number of KOI-7016. Planetary candidates were detected around the star by NASAs Kepler Mission, the transit method that Kepler uses involves detecting dips in brightness in stars. Following the acceptance of the paper, the Kepler team provided an additional moniker for the system of Kepler-452. The discoverers referred to the star as Kepler-452, which is the procedure for naming the exoplanets discovered by the spacecraft. Hence, this is the used by the public to refer to the star. Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations.01 etc. after the stars name, if planet candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest. Following these rules, there was one candidate planet detected. The name Kepler-452 derives directly from the fact that the star is the catalogued 452nd star discovered by Kepler to have confirmed planets, the designation b, derives from the order of discovery. The designation of b is given to the first planet orbiting a given star, in the case of Kepler-452, there was only one planet, so only the letter b is used. Kepler-452 is a G-type star that is approximately 104% the mass of and it has a temperature of 5757 K and is roughly 6 billion years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K, the star is metal-rich, with a metallicity of about 0.21, or about 162% of the amount of iron and other heavier metals found in the Sun. The stars luminosity is somewhat normal for a star like Kepler-452, the stars apparent magnitude, or how bright it appears from Earths perspective, is 13.426. Therefore, it is too dim to be seen with the naked eye and this chart compares the Sun to Kepler-452

30.
Kapteyn b
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Kapteyn b is a possible exoplanet that orbits within the habitable zone of the red subdwarf Kapteyns star, located approximately 12.8 light-years from Earth. Kapteyn b is within the habitable zone of its star. It was the closest suspected potentially habitable exoplanet to the Solar System other than Tau Ceti e up until 2016, however, later research has cast doubt on the existence of Kapteyn b, suggesting the signal is consistent with stellar activity rather than a planet. The system itself is estimated to be 11 billion years old, Kapteyn b is a super-Earth, a planet that has a radius and mass bigger than that of Earth, but smaller than that of the ice giants Uranus and Neptune. It has a temperature of 205 K. It has a greater than that or equal to 4.8 M⊕. The planet orbits a red subdwarf star named Kapteyns Star, the star has a mass of 0.27 M☉ and a radius 0.29 R☉. It has a surface temperatures of 3550 K and is roughly 11 billion years old, in comparison, the Sun is about 4.6 billion years old and has a surface temperature of 5778 K. The stars apparent magnitude, or how bright it appears from Earths perspective, is 8.85 and it is too dim to be seen with the naked eye, but can be seen with good binoculars. It has an eccentricity of 0.21, meaning its orbit is mildly elliptical, Kapteyn b has a radius range of 1. 2–1.6 R⊕, so it is likely rocky. Its host star is a red subdwarf, with a more than a quarter as much mass then the Sun does. As a result, stars like Kapteyns Star have the ability to live up to 100–200 billion years, another crucial factor in habitability is temperature and atmospheric properties. The estimated equilibrium temperature for Kapteyn b is around 205 K, without the proper greenhouse gases in its atmosphere, it is likely to be a planet covered in ice. However, if it has enough CO2 in its atmosphere, the temperature may rise enough to have water exist in its liquid form on the surface. The planet was first discovered by the HARPS spectrometer which is housed at the European Southern Observatorys La Silla Observatory in Chile, further confirmations of the planetary detection were made at the Keck Observatory in Hawaii and at the PFS Observatory, also in Chile. The method of discovery involved observing and recording tiny wobbles in the star caused by the tug of its planets. One other planet has been detected within the planetary system. It is designated Kapteyn c and orbits further out from the star and it is considered to be too cold for stellar-light based life

31.
Kapteyn's Star
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Kapteyns Star is a class M1 red subdwarf about 12.76 light years from Earth in the southern constellation Pictor, it is the closest halo star to the Solar System. With a magnitude of nearly 9 it is visible through binoculars or a telescope and its diameter is 30% of the Suns, but its luminosity just 1. 2% that of the Suns. It may have once been part of the globular cluster Omega Centauri, the discovery of two planets — Kapteyn b and Kapteyn c — was announced in 2014. Attention was first drawn to what is now known as Kapteyns Star by the Dutch astronomer Jacobus Kapteyn in 1898, under the name CPD-44612 it was included in the Cape photographic Durchmusterung for the equinox 1875 by David Gill and Jacobus Cornelius Kapteyn in 1897. This catalogue was based on Gills observations from the Cape Observatory in 1885—1889 and was created in collaboration with Kapteyn, while he was reviewing star charts and photographic plates, Kapteyn noted that a star, previously catalogued in 1873 by B. A. Gould as C. Z. V243, seemed to be missing, Innes found an uncatalogued star about 15 arc seconds away from the absent stars position. It became clear that the star had, in fact, a high proper motion of more than 8 arc seconds per year and had moved significantly in the meantime. Later, CPD-44612 came to be referred to as Kapteyns Star although it is clear that equal credit should be accorded to Robert Innes, at the time of its discovery, it had the highest proper motion of any star known, dethroning Groombridge 1830. With the discovery of Barnards Star in 1916, Kapteyns Star dropped to second place, in 2014, two super-Earth planet candidates in orbit around the star were announced. Based upon parallax measurements with the Hipparcos astrometry satellite, Kapteyns Star is at a distance of 12.76 light-years from the Earth and it came within 7.00 light-years of the Sun about 10,800 years ago and has been moving away since that time. The stellar classification is sdM1, which indicates that it is a subdwarf with a luminosity lower than that of a star at the same spectral type of M1. The abundance of other than hydrogen and helium, what astronomers term the metallicity, is about 14% of the abundance in the Sun. It is a star of the BY Draconis type with the identifier VZ Pictoris. Kapteyns Star is distinctive in a number of other regards, it has a radial velocity, orbits the Milky Way retrograde. It is a member of a group of stars that share a common trajectory through space. Based upon their element abundances, these stars may once have been members of Omega Centauri, during this process, the stars in the group, including Kapteyns Star, may have been stripped away as tidal debris. The star is at an apparent magnitude of 9 and is visible through binoculars or a telescope in the constellation of Pictor, in the southern sky, in 2014, Kapteyns Star was announced to host two planets, Kapteyn b and Kapteyn c. Kapteyn b is the potentially habitable planet, estimated to be 11 billion years old

32.
Kepler-62
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Kepler-62 is a star somewhat cooler and smaller than the Sun in the constellation Lyra,1,200 light years from Earth. It is located within the field of vision of the Kepler spacecraft, on April 18,2013 it was announced that the star has five planets, two of which, Kepler-62e and Kepler-62f are within the stars habitable zone. The outermost, Kepler-62f, is likely a rocky planet, prior to Kepler observation, Kepler-62 had the 2MASS catalogue number 2MASS J18525105+4520595. In the Kepler Input Catalog it has the designation of KIC9002278, Planetary candidates were detected around the star by NASAs Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars, following the acceptance of the discovery paper, the Kepler team provided an additional moniker for the system of Kepler-62. The discoverers referred to the star as Kepler-62, which is the procedure for naming the exoplanets discovered by the spacecraft. Hence, this is the used by the public to refer to the star. Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations.01.02.03.04.05 etc. after the stars name, in the order of discovery. If planet candidates are detected simultaneously, then the ordering follows the order of periods from shortest to longest. The designations b, c, d, e, and f derive from the order of discovery, the designation of b is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet. In the case of Kepler-62, all of the planets in the system were announced at one time, so b is applied to the closest planet to the star. The name Kepler-62 derives directly from the fact that the star is the catalogued 62nd star discovered by Kepler to have confirmed planets, Kepler-62 is a K-type main sequence star star that is approximately 69% the mass of and 64% the radius of the Sun. It has a temperature of 4925 K and is 7 billion years old, in comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K. The star is somewhat poor in metals, with a metallicity of about –0.37, or about 42% of the amount of iron, the stars luminosity is typical for a star like Kepler-62, with a luminosity of around 21% of that of the solar luminosity. The stars apparent magnitude, or how bright it appears from Earths perspective, is 13.75, therefore, it is too dim to be seen with the naked eye. All known planets transit the star, this means that all five planets orbits appear to cross in front of their star as viewed from the Earths perspective. Their inclinations relative to Earths line of sight, or how far above or below the plane of sight they are and this allows direct measurements of the planets periods and relative diameters by monitoring each planets transit of the star. The radii of the fall between 0.54 and 1.95 Earth radii

33.
Kepler-186
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Kepler-186 is a main-sequence M1-type dwarf star, located 151 ±18 parsecs away in the constellation of Cygnus. The star is cooler than the sun, with roughly half its metallicity. It is known to have five planets, including the first Earth-sized world discovered in the habitable zone, the star hosts four other planets discovered so far, though Kepler-186 b, c, and d are too close, but e is near the habitable zones inner edge. A number of previously unknown measurements of the star are known, in the infrared/microwave EM spectrum its H band magnitude is 11.605, J band magnitude is 12.473, and its K band magnitude is 11.605. In the visual Photometric system magnitude it is 14.90 and 16.40 It is a BY Draconis variable changing brightness slightly, probably from starspots, with a period of 33.695 days. The star is Red dwarf/M-class bordering on being an Orange dwarf/K-class star, with a nearly half that of the Suns. Within two first years of gathered data, the signals of four inner planetary candidates were found, discussion of planets in the system was taking place in August and November 2013. In February 2014, those planets were confirmed through the verification by multiplicity method, the fifth outermost candidate was confirmed in the same manner in April 2014. The five planets discovered around Kepler-186 are all expected to have a solid surface, the smallest one, Kepler-186b, is only 8% larger than Earth, while the largest one, Kepler-186d, is almost 40% larger. Because of the slow evolution of red dwarf stars, the age of the Kepler-186 system is poorly constrained. There is a roughly 50-50 chance it is tidally locked, since it is closer to its star than Earth is to the Sun, it will probably rotate much more slowly than Earth, its day could be weeks or months long. Planetary formation simulations have shown that there could be one additional non-transiting low-mass planet between Kepler-186e and Kepler-186f. If this planet exists, it is not much more massive than Earth. If it were, its influence would likely prevent Kepler-186f from transiting. Conjectures involving the Titius–Bode law, indicate that there could be several remaining planets to be found in the system - two small ones between e and f and another one outside of f. Low metallicity of the star, at -, thus Kepler 186 started as KIC8120608 and then was identified as KOI571. Outside of the Kepler project, the 2MASS survey catalogued this star as 2MASS J19543665+4357180

Exoplanets
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An exoplanet or extrasolar planet is a planet that orbits a star other than the Sun. The first scientific detection of an exoplanet was in 1988, HARPS has discovered about a hundred exoplanets while the Kepler space telescope has found more than two thousand. Kepler has also detected a few thousand candidate planets, of which about 11% may be false

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Artist's view gives an impression of how commonly planets orbit the stars in the Milky Way.

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The three known planets of the star HR8799, as imaged by the Hale Telescope. The light from the central star was blanked out by a vector vortex coronagraph.

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2MASS J044144 is a brown dwarf with a companion about 5–10 times the mass of Jupiter. It is not clear whether this companion object is a sub-brown dwarf or a planet.

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Coronagraphic image of AB Pictoris showing a companion (bottom left), which is either a brown dwarf or a massive planet. The data was obtained on 16 March 2003 with NACO on the VLT, using a 1.4 arcsec occulting mask on top of AB Pictoris.

University of Puerto Rico at Arecibo
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The University of Puerto Rico at Arecibo is a state university located in the city of Arecibo, Puerto Rico, and part of the eleven campuses that compose the University of Puerto Rico system. UPR-Arecibo is known from its previous names Colegio Regional de Arecibo and Colegio Universitario Tecnológico de Arecibo and its acronyms CRA and it is accred

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Main building

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University of Puerto Rico at Arecibo

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UPRA

Planetary habitability
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Planetary habitability is the measure of a planets or a natural satellites potential to have habitable environments hospitable to life. Habitable environments do not need to contain life, Life may develop directly on a planet or satellite or be transferred to it from another body, a hypothetical process known as panspermia. Research and theory in t

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Understanding planetary habitability is partly an extrapolation of the conditions on Earth, as this is the only planet known to support life.

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The moons of some gas giants could potentially be habitable.

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Mars, with its rarefied atmosphere, is colder than the Earth would be if it were at a similar distance from the Sun.

Geophysics
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Although geophysics was only recognized as a separate discipline in the 19th century, its origins date back to ancient times. The first magnetic compasses were made from lodestones, while more modern magnetic compasses played an important role in the history of navigation, the first seismic instrument was built in 132 BC. Geophysics is applied to s

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Illustration of the deformations of a block by body waves and surface waves (see seismic wave).

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Age of the sea floor. Much of the dating information comes from magnetic anomalies.

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Replica of Zhang Heng 's seismoscope, possibly the first contribution to seismology.

Geodynamics
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Geodynamics is a subfield of geophysics dealing with dynamics of the Earth. It also attempts to probe the internal activity by measuring magnetic fields, gravity, methods of geodynamics are also applied to exploration of other planets. Geodynamics is generally concerned with processes that move throughout the Earth. In the Earth’s interior, movemen

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Geodesy

Plasma (physics)
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Plasma is one of the four fundamental states of matter, the others being solid, liquid, and gas. Yet unlike these three states of matter, plasma does not naturally exist on the Earth under normal surface conditions, the term was first introduced by chemist Irving Langmuir in the 1920s. However, true plasma production is from the separation of these

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Plasma

Habitable zone
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The bounds of the CHZ are based on Earths position in the Solar System and the amount of radiant energy it receives from the Sun. Since the concept was first presented in 1953, many stars have been confirmed to possess a CHZ planet, most such planets, being super-Earths or gas giants, are more massive than Earth, because such planets are easier to

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Natural defenses against space weather, such as the magnetosphere depicted in this artistic rendition, may be required for planets to sustain surface water for prolonged periods.

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An example of a system based on stellar luminosity for predicting the location of the habitable zone around various types of stars. Planet sizes, star sizes, orbit lengths, and habitable zone sizes are not to scale.

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Earth's hydrosphere. Water covers 71% of Earth's surface, with the global ocean accounting for 97.3% of the water distribution on Earth.

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Artists concept of a planet on an eccentric orbit that passes through the CHZ for only part of its year

Astronomy
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Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets, while the phenomena include supernovae explosions, gamma ray burs

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A star -forming region in the Large Magellanic Cloud, an irregular galaxy.

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A giant Hubble mosaic of the Crab Nebula, a supernova remnant

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19th century Sydney Observatory, Australia (1873)

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19th century Quito Astronomical Observatory is located 12 minutes south of the Equator in Quito, Ecuador.

Astrobiology
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Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe, extraterrestrial life and life on Earth. Astrobiology addresses the question of whether life exists beyond Earth, the origin and early evolution of life is an inseparable part of the discipline of astrobiology. Although speculation is entertained t

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It is not known whether life elsewhere in the universe would utilize cell structures like those found on Earth. (Chloroplasts within plant cells shown here.)

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In June 2014, the John W. Kluge Center of the Library of Congress held a seminar focusing on astrobiology. Panel members (L to R) Robin Lovin, Derek Malone-France, and Steven J. Dick

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The illustration on the Pioneer plaque

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Artist's impression of the extrasolar planet OGLE-2005-BLG-390Lb orbiting its star 20,000 light-years from Earth; this planet was discovered with gravitational microlensing.

Star
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It is primarily present in steroid-producing cells, including theca cells and luteal cells in the ovary, Leydig cells in the testis and cell types in the adrenal cortex. The aqueous phase between two membranes cannot be crossed by the lipophilic cholesterol, unless certain proteins assist in this process. It is now clear that this process is mediat

Planet
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International

Terrestrial planet
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A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the planets are the inner planets closest to the Sun, i. e. Mercury, Venus, Earth. The terms terrestrial planet and telluric planet are derived from Latin words for Earth, as these planets are, in terms

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Relative masses of the terrestrial planets of the Solar System, including the Moon (designated here as "Luna")

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Sizes of Kepler planet candidates based on 2,740 candidates orbiting 2,036 stars as of November 4, 2013 (NASA).

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Artist's impression of a carbon planet

Earth analog
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An Earth analog is a planet or moon with environmental conditions similar to those found on the planet Earth. The possibility is of particular interest to astronomers under reasoning that the more similar a planet is to Earth, as such, it has long been speculated and the subject expressed in science, philosophy, science fiction and popular culture.

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The planet Earth

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Percival Lowell depicted Mars as a dry but Earth-like planet and habitable for an extraterrestrial civilisation

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Size Comparisons: Kepler-20e and Kepler-20f with Venus and Earth.

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Surfaces like this of Saturn's moon Titan (taken by Huygens probe) bear superficial similarities to the floodplains of Earth

Kepler (spacecraft)
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Kepler is a space observatory launched by NASA to discover Earth-size planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched on March 7,2009 and these data are transmitted to Earth, then analyzed to detect periodic dimming caused by exoplanets that cross in front of their host star. Kepler is part of NASAs

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Artist's impression of the Kepler telescope

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Kepler in Astrotech's Hazardous Processing Facility

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Kepler ‍‍ '​‍s search volume, in the context of the Milky Way galaxy.

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Kepler ‍‍ '​‍s launch on March 7, 2009

Extrasolar planets
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An exoplanet or extrasolar planet is a planet that orbits a star other than the Sun. The first scientific detection of an exoplanet was in 1988, HARPS has discovered about a hundred exoplanets while the Kepler space telescope has found more than two thousand. Kepler has also detected a few thousand candidate planets, of which about 11% may be false

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Artist's view gives an impression of how commonly planets orbit the stars in the Milky Way.

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The three known planets of the star HR8799, as imaged by the Hale Telescope. The light from the central star was blanked out by a vector vortex coronagraph.

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2MASS J044144 is a brown dwarf with a companion about 5–10 times the mass of Jupiter. It is not clear whether this companion object is a sub-brown dwarf or a planet.

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Coronagraphic image of AB Pictoris showing a companion (bottom left), which is either a brown dwarf or a massive planet. The data was obtained on 16 March 2003 with NACO on the VLT, using a 1.4 arcsec occulting mask on top of AB Pictoris.

Solar analog
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Solar-type star, solar analogs, and solar twins are stars that are particularly similar to the Sun. The stellar classification is a hierarchy with solar twin being most like the Sun followed by solar analog, Observations of these stars are important for understanding better the properties of the Sun in relation to other stars and the habitability o

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The Sun (left) compared to the similar but slightly smaller and less active Tau Ceti (right).

Red dwarf
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In May 2015, it was announced that Series XI and XII would film back-to-back later in 2015 and would air exclusively on the Dave channel in 2016 and 2017. The first episode of Red Dwarf XI aired at 9 p. m. on Thursday 22 September 2016 on Dave and has been available via streaming service UKTV Play from Thursday 15 September 2016, the series was cre

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The second Red Dwarf ship model as used for series 5.

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From left to right: Kryten, Lister, Cat, and Rimmer as they appeared in 2009's Back to Earth.

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The episode " Polymorph " parodied the 1979 Alien film

Milky Way
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The Milky Way is the galaxy that contains our Solar System. The descriptive milky is derived from the appearance from Earth of the galaxy – a band of light seen in the night sky formed from stars that cannot be distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from Earth, the Milky Way appears as a band be

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The Milky Way's Galactic Center in the night sky above Paranal Observatory (the laser creates a guide-star for the telescope).

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A view of the Milky Way toward the constellation Sagittarius (including the Galactic Center) as seen from an area not polluted by light (the Black Rock Desert, Nevada)

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The Milky Way arching at a high inclination across the night sky (fish-eye mosaic shot at Paranal, Chile).

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A photograph of galaxy NGC 6744, which might resemble the Milky Way.

Kepler-62f
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Kepler-62f is a super-Earth exoplanet orbiting within the habitable zone of the star Kepler-62, the outermost of five such planets discovered by NASAs Kepler spacecraft. It is located about 1,200 light-years from Earth in the constellation of Lyra, the exoplanet was found by using the transit method, in which the dimming effect that a planet causes

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Comparison of the sizes of planets Kepler-69c, Kepler-62e, Kepler-62f, and the Earth. (Exoplanets are artists' conceptions.)

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The Kepler Space Telescope search volume, in the context of the Milky Way Galaxy.

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Launches

Kepler-186f
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Kepler-186f is an exoplanet orbiting the red dwarf Kepler-186, about 500 light-years from the Earth. It is the first planet with a similar to Earths to be discovered in the habitable zone of another star. NASAs Kepler spacecraft detected it using the method, along with four additional planets orbiting much closer to the star. Analysis of three year

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Comparison of the Kepler-186 system and the Solar System (17 April 2014)

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Artist's concept of a rocky Earth -sized exoplanet in the habitable zone of its host star, possibly compatible with Kepler-186f’s known data (NASA/SETI/JPL)

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Space probes

Kepler-442b
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The planet was discovered by NASAs Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the confirmation of the exoplanet on 6 January 2015, Kepler-442b is a super-Earth, an exoplanet with a mass and radius bigger than that of Earth, but smaller t

Star type
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In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with absorption lines, each line indicates an ion of a certain chemical ele

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Secchi spectral types (152 Schjellerup is Y Canum Venaticorum)

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Hertzsprung–Russell diagram

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Artist's impression of Aludra, a B5 supergiant

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Fomalhaut, an A3 main-sequence star

Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths g

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" The Blue Marble " photograph of Earth, taken during the Apollo 17 lunar mission in 1972

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Artist's impression of the early Solar System's planetary disk

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World map color-coded by relative height

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The summit of Chimborazo, in Ecuador, is the point on Earth's surface farthest from its center.

Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accou

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The Sun in visible wavelength with filtered white light on 8 July 2014. Characteristic limb darkening and numerous sunspots are visible.

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During a total solar eclipse, the solar corona can be seen with the naked eye, during the brief period of totality.

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Taken by Hinode 's Solar Optical Telescope on 12 January 2007, this image of the Sun reveals the filamentary nature of the plasma connecting regions of different magnetic polarity.

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Visible light photograph of sunspot, 13 December 2006

Proxima Centauri
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Proxima Centauri or Alpha Centauri C is a red dwarf, a small low-mass star, about 4.25 light-years from the Sun in the constellation of Centaurus. It was discovered in 1915 by the Scottish astronomer Robert Innes, the Director of the Union Observatory in South Africa, with an apparent magnitude of 11.05, it is too faint to be seen with the naked ey

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Proxima Centauri as seen by Hubble

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The two bright stars are (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri.

Gliese 667 Cc
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The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planets parent star. Gliese 667 Cc is a super-Earth, an exoplanet with a mass and radius greater than that of Earth and it is heavier than Earth with a minimum mass of about 3.7 Earth masses. The eq

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An artist’s impression of a sunset on Gliese 667 Cc as an Earth-like planet.

Gliese 667 C
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Gliese 667 is a triple-star system in the constellation of Scorpius lying at a distance of about 6.8 pc from Earth. All three of the stars have masses smaller than the Sun, there is a 12th magnitude star close to the other three, but it is not gravitationally bound to the system. To the naked eye, the system appears to be a faint star of magnitude

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Artist's impression of Gliese 667 Cb with the Gliese 667 A/B binary in the background

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A star chart of the constellation of Scorpius showing the position of Gliese 667

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An artist's impression of GJ 667 Cc, a potentially habitable planet orbiting a red dwarf constituent in a trinary star system

Kepler-452b
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Kepler-452b is an exoplanet orbiting the Sun-like star Kepler-452 about 1,400 light-years from Earth in the constellation Cygnus. It was identified by the Kepler space telescope, and its discovery was announced by NASA on 23 July 2015 and it is the first potentially rocky super-Earth planet discovered orbiting within the habitable zone of a star ve

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Artist's concept of Kepler-452b

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Comparison of small planets found by Kepler in the habitable zone of their host stars.

Kepler-452
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Kepler-452 is a G-type main-sequence star located about 1400 light-years away from Earth in the constellation of Cygnus. It has a temperature to that of the Sun. It is approximately six years old,1.5 billion years older than the Sun. Thus, Kepler-452 can be considered a twin, however its age pushes it more back towards the solar analog criteria. Pr

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A diagram of the Kepler-452b System, compared to our Inner Solar System and the Kepler-186 system.

Kapteyn b
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Kapteyn b is a possible exoplanet that orbits within the habitable zone of the red subdwarf Kapteyns star, located approximately 12.8 light-years from Earth. Kapteyn b is within the habitable zone of its star. It was the closest suspected potentially habitable exoplanet to the Solar System other than Tau Ceti e up until 2016, however, later researc

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Space probes

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Orbit of Kapteyn b

Kapteyn's Star
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Kapteyns Star is a class M1 red subdwarf about 12.76 light years from Earth in the southern constellation Pictor, it is the closest halo star to the Solar System. With a magnitude of nearly 9 it is visible through binoculars or a telescope and its diameter is 30% of the Suns, but its luminosity just 1. 2% that of the Suns. It may have once been par

Kepler-62
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Kepler-62 is a star somewhat cooler and smaller than the Sun in the constellation Lyra,1,200 light years from Earth. It is located within the field of vision of the Kepler spacecraft, on April 18,2013 it was announced that the star has five planets, two of which, Kepler-62e and Kepler-62f are within the stars habitable zone. The outermost, Kepler-6

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The Kepler Space Telescope search volume, in the context of the Milky Way.

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Star Systems - Kepler-62 System and the Solar System

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Planet Sizes - Kepler-69c, Kepler-62e, Kepler-62f, and Earth.

Kepler-186
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Kepler-186 is a main-sequence M1-type dwarf star, located 151 ±18 parsecs away in the constellation of Cygnus. The star is cooler than the sun, with roughly half its metallicity. It is known to have five planets, including the first Earth-sized world discovered in the habitable zone, the star hosts four other planets discovered so far, though Keple

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The orbit of GJ 832 c around its parent star, with the habitable zone boundaries shown. Planet c's orbit is rather eccentric and takes it in and out of the range of the habitable zone at different parts of its orbit, possibly leading to extreme seasons.

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Artist's view gives an impression of how commonly planets orbit the stars in the Milky Way.

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The three known planets of the star HR8799, as imaged by the Hale Telescope. The light from the central star was blanked out by a vector vortex coronagraph.

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2MASS J044144 is a brown dwarf with a companion about 5–10 times the mass of Jupiter. It is not clear whether this companion object is a sub-brown dwarf or a planet.

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Coronagraphic image of AB Pictoris showing a companion (bottom left), which is either a brown dwarf or a massive planet. The data was obtained on 16 March 2003 with NACO on the VLT, using a 1.4 arcsec occulting mask on top of AB Pictoris.

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This map shows all of the star systems within 14 light-years of the Sun (shown as Sol), except for brown dwarfs discovered after 2009. Double and triple stars are shown "stacked", but the true location is the star closest to the central plane. Color corresponds to the table above.

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The Moon, Io, and Earth shown to scale. Although significantly smaller, some of the Solar System's moons and dwarf planets share similarities to Earth's density and temperature resulting in relatively high ESIs. It is theoretically possible for Earth-sized extrasolar moons and other non-planets to have high ESIs.

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The Rare Earth Hypothesis argues that planets with complex life, like Earth, are exceptionally rare

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The dense centre of galaxies such as NGC 7331 (often referred to as a "twin" of the Milky Way) have high levels of radiation which are dangerous to complex life

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According to Rare Earth, globular clusters are unlikely to support life.

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Depiction of the Sun and planets of the Solar System and the sequence of planets. Rare Earth argues that without such an arrangement, in particular the presence of the massive gas giant Jupiter (fifth planet from the Sun and the largest), complex life on Earth would not have arisen.